A closer inspection of the data, however, shows the share held by V- and Z-rated tires has plateaued at OE at roughly 20% but continues to grow steadily in the replacement market, topping the 20% mark for the first time in 2017.
One explanation for the seeming OE anomaly is the industry's shift to SUVs and CUVs and away from traditional performance-oriented coupes and sedans. In fact, the V/Z-rated share hit 20 percent in 2013, then dipped under that plateau in 2014-16 before rebounding slightly last year.
It should be noted USTMA data refer only to shipments going to the global car makers' North American assembly plants. Vehicles imported from outside North America — which accounted for 23% of US car sales last year — are not included in the numbers.
Aftermarket shipments in the US of tires H-rated and higher rose 9.1% last year to 92 million units, a volume that represents 44% of all aftermarket shipments, up from 41% in 2016.
Viewed more closely, aftermarket shipments of H-rated tires rose 11.7% to 48.8 million units; V-rated tires rose 8.4% to 25.8 million units; and Z-rated were up 3.6% to 17.4 million units.
The share of the OE segment held by performance tires jumped 5 points last year vs. 2016 to 55.8%, USTMA data reveal, even though shipments to OE customers slipped 4.1% to 25.2 million units.
The share rose because overall shipments of OE passenger tires to North American light vehicle producers fell even more, 6.9%, reflecting a drop in production in 2017 in North America of cars, SUVs, light trucks, etc. to 17.2 million units.
The shift at OE is also reflected in the breakdown of OE tire sizes, where the 10 most popular sizes are now all 17-, 18- or 20-inch rim diameter sizes, including two — 235/60R18 and 245/60R18 — that are new to the top 10.
The replacement market lags OE in this regard, with no 18-inch sizes and two 15-inch sizes — 195/65R15 and 195/60R15 — still among the 10 most prevalent sizes, USTMA data reveal.
Imports of tires with rim diameters of 17 inches and greater jumped 13% last year over 2016 to 46 million units, according to US Department of Commerce data.
The import data show speed ratings, so tires of this size don't necessarily correspond to the H-rated and above category. But a general comparison can be made, showing that imports represent roughly half of the performance tire category.
There's a stark contrast, however, in the value of imported tires in the larger rim-sizes, the data show.
The average declared customs value of a tire in this grouping was $68.18, according to the data, but the range extends from $34.88 on the low end (China) to more than $100 on the high end (France, Germany and Italy).
Thailand, South Korea and Mexico are the three largest sources of tires in the 17-inch and larger categories.